The present invention relates to an apparatus movably adhering to the vertical or inclined walls of large structures such as ships, oil-tanks or the like and movable in the desired direction by applying magnetic or vacuum adhering means thereto.
Conventionally, various apparatus for moving on the walls in the desired direction by remote-control and having affixed thereto a cleaning apparatus such as a steel grit blasting device or coating device have been proposed for the purpose of removing rust, stains and paint from the walls of the aforementioned large structures or for finishing and coating bead welds thereon. The above-mentioned conventional apparatus, however, have the following common disadvantages. Firstly, though they utilize the attractive force of electro-magnets or vacuum, the above attractive force is employed to the extent of preventing them from separating from the walls freely and they are not employed effectively and positively. Accordingly, they do not always hold and attain a complete adhering condition to the walls. It is a matter of general knowledge that the magnetic force falls off extremely in inverse proportion to the space or distance between the magnet and the wall, as shown in FIG. 4. Therefore, it is desired to utilize the character of a magnet as much as possible and this is the same with regard to the vacuum force.
Secondly, due to the incomplete utilization of the above attractive force, the hoisting and shifting device for suspending and leading the above movable apparatus and the cleaning apparatus are indispensable to avoid having the movable apparatus fall along with the cleaning apparatus in the case where the latter is used. That is, it is necessary to set up hoisting and shifting device on the deck or to provide cranes in the vicinity of the walls. This results in the working condition becoming burdensome, so that it is desired to simplify and omit these preparative conditions as much as possible.
Thirdly, conventional movable apparatus can scarcely move on curved or uneven walls such as the bow or the stern of a ship's hull. Therefore, these conventional movable apparatus could not improve their working efficiency contrary to expectations, and have been employed within narrow limits because of the above mentioned disadvantages.